Past studies demonstrate that one effect of ethanol (body temperature change during intoxication) can strongly influence sensitivity to other effects of ethanol and can alter genetically determined differences in brain sensitivity to ethanol. However, little is known about the cellular mechanisms by which temperature affects ethanol sensitivity and the role temperature plays in mediating differences in ethanol sensitivity established by selective breeding. In addition, recent studies indicate that temperature can significantly influence the sensitivity of in vitro systems to ethanol, but systematic information is not available. These gaps in our knowledge cloud interpretation of many ethanol studies. The present proposal addresses these issues. Specific Aim 1 tests the hypothesis that ethanol-induced changes in body temperature during intoxication mediate genetically determined differences in ethanol sensitivity established by selective breeding. We will accomplish this goal by determining ethanol sensitivity in the presence and absence of ethanol-induced hypothermia in selectively bred animals commonly used in ethanol research [Withdrawal Seizure Prone (WSP) and Resistant (WSR) mice and High Alcohol Sensitive (HAS) and Low Alcohol Sensitive (LAS) rats]. We will measure ethanol sensitivity using the respective measure upon which selection pressure was placed to establish the line (withdrawal seizures and loss of righting reflex.) Body temperatures and blood and brain ethanol concentrations will be determined. These studies, in conjunction with our previous work, will provide a definitive test of the hypothesis. Specific Aim 2 investigates the mechanisms of temperature's effects on brain sensitivity to ethanol by testing hypothesis that specific cellular systems are involved. In addition, Aim 2 will systematically test the hypothesis that temperature is a critical variable in vitro studies of ethanol's cellular actions and effects. We will Aim 2's overlapping goals by studying the effects of temperature (23-38 degrees C) and ethanol (12.5- 400 Mm) in vitro on cellular systems implicated in mediating or modulating ethanol's behavioral effects [membrane order (polarization of fluorescent probes), GABA-A stimulated 36 C1- uptake, NMDA-stimulated dopamine release and NMDA mediated dendritic EPSPs]. Aim 2's experiments will test four mouse genotypes with demonstrated differences in the qualitative effects of temperature on their behavioral sensitivities to ethanol (C57BL,129,LS and SS mice) in order to determine whether genotypic differences in the effects of temperature on ethanol sensitivity in specific cellular systems exist and may underlie their differences in temperature's effects on ethanol sensitivity in vivo. Overall, the proposed research will provide essential information which will enhance the use of pharmacogenetic tools and in vitro techniques in ethanol research and will also contribute to our long term objectives which are to understand the importance and mechanisms of temperature's effects on ethanol sensitivity.